1. FIELD OF THE INVENTION
The present invention relates to an ignition timing control apparatus for a non-distribution type internal combustion engine in which ignition of the cylinders is effected without using a distributer.
2. DISCUSSION OF BACKGROUND
As an example of an ignition timing control apparatus of this kind, FIG. 13 shows a control apparatus for a four-cycle engine. In FIG. 13, a reference numeral 1 designates a signal generating means which has the construction as shown in FIG. 14. A reference numeral 2 designates a signal rotor rotating in synchronism with the revolution of the internal combustion engine. A trigger pole 3 is attached on the outer circumference of the signal rotor 2. A pair of signal coils 4a, 4b are provided at phase angle positions of 180.degree. with respect to the signal rotor 2 and facing the trigger pole 3. The output terminals of the signal coils 4a, 4b are respectively connected to waveform shaping circuits 5a, 5b which are, in turn, connected to an ignition timing operating device 6. Reference numerals 7a, 7b respectively designate amplifying circuits for amplifying the outputs of the ignition timing operating device, which are respectively connected to the primary coils of the ignition coils 8a, 8b. The output terminals of the secondary coil of the ignition coil 8a are respectively connected to the ignition plug 9a for the first cylinder and the ignition plug 9b for the fourth cylinder. The output terminals of the secondary coil of the ignition coil 8b are respectively connected to the ignition plug 9c for the second cylinder and the ignition plug 9d for the third cylinder.
The operation of the ignition control apparatus having the above-mentioned construction will be described with reference to a timing chart as in FIG. 15 in which reference characters a-h respectively designate signals generated at the positions a-h in the apparatus and the device shown in FIGS. 13 and 14.
When the signal rotor 2 is rotated in the arrow mark direction in synchronism with the revolution of the engine, an angle signal including positive and negative pulses is generated from the signal coil 4a as shown in FIG. 15a, and an angle signal including positive and negative pulses is generated from the signal coil 4b as shown in FIG. 15b. The later angle signal has a phase lag of 180.degree.with respect to the former. These angle signals are respectively subjected to waveform-shaping in the waveform shaping circuits 5a, 5b and are outputted in a form of rectangular signals as shown in FIG. 15c and 15d. The ignition timing operating device 6 performs predetermined operations for ignition timing on the basis of the rectangular signals, whereby ignition timing control signals as shown in FIGS. 15e and 15f are outputted. The ignition timing control signals are respectively amplified in the amplifying circuits 7a and 7b to be used to continue and break the electric conduction to the ignition coils 8a, 8b. The waveform of currents supplied to the primary coils of the ignition coils 8a, 8b are respectively shown in FIGS. 15g and 15h. A high voltage is produced at the secondary coils when the currents are interrupted, whereby spark discharging is respectively resulted at each group of ignition plugs 9a, 9b and 9c, 9d so that the corresponding cylinders are ignited at predetermined periods of ignition timing. In the embodiment as shown in FIGS. 13 through 15, the spark discharging takes place for the groups of the first and the fourth cylinders and the second and third cylinders simultaneously. In this case, when one group of cylinders is in an explosion process, the other group is in a discharging process. Accordingly, the spark discharging for the cylinders in the discharging process does not contribute to ignition.
FIG. 16 shows an example of a signal generating means for a 90.degree.V-type two cycle engine. The structure of an ignition timing control apparatus including the signal generating means is the same as that shown in FIG. 13 provided that it has no ignition plugs 9c and 9d.
As shown in FIG. 16, a single trigger pole 3 is attached on the signal rotor 2, and the signal coils 4a, 4b are provided to have a phase difference of 90.degree.with respect to the signal rotor 2 and facing the trigger pole 3, whereby there produces a signal having a leg of 90.degree.from the signal coil 4b with respect to a signal from the signal coil 4a. The ignition timing control apparatus produces signals having the waveforms as shown in FIG. 17a through 17h, whereby spark discharging is effected for the ignition plugs 9a, 9b.
FIG. 18 shows a signal generating means for a 75.degree.V-type two cycle engine. An ignition timing control apparatus including the signal generating means is the same as that shown in FIG. 13 provided that it has no ignition plugs 9c and 9d.
As shown in FIG. 18, a single trigger pole 3 is attached on the signal rotor 2, and signal coils 4a, 4b are provided at positions to have a phase difference of 75.degree.on the signal rotor 2 and facing the trigger pole 3. The ignition timing control apparatus produces signals. The waveforms of these signals are the same as shown in FIG. 17 except that the phase of angle signals is different.
In the conventional ignition timing control apparatus having the above-mentioned construction, a space is required for the coils corresponding to the number of cylinders. This opposes requirement for reducing the size an internal combustion engine. Further, the manufacturing cost of the engine is increased by providing the signal coils in correspondence to the number of cylinders.
There is another proposal as disclosed in Japanese Examined Pat. Publication No. 1350/1984 or Japanese Examined Patent Publication No. 49427/1984 that a number of trigger poles are attached on the outer circumference of a signal rotor at equal distances so that ignition timing control signals are distributed to the ignition coils by a signal generated from a signal coil. However, the proposed apparatus required an additional signal coil to detect a reference position of the signal rotor. Further, the construction of the ignition timing operating device was complicated. In addition, since operations for estimation of ignition timing were conducted by an angle signal by using a trigger pole 3 or trigger poles 3, the ignition timing became incorrect due to change in revolution of a V-type engine.